[Q&A] Medicine Step 2. Answer 1

Section: Trauma (html comment removed: - Subject/title )

Question: A 74 year old gentleman arrives in the emergency department trauma bay an hour after having fallen down in the stands at a baseball game. Per his wife, he fell hard on his left hip and she heard a "pop." After 4 hours of waiting, he develops sudden shortness of breath.

The intern performs a quick exam, noting a shortened and everted left leg. The man experiences sharp pains with any movement, without loss of sensation. There is no external bleeding or purpura. Vital signs are BP 160/100, P 100, RR 24 SpO2 84%, T 37. Lung sounds are clear bilaterally. What is the most likely etiology of the patient's shortness of breath? (html comment removed: - Prompt )

The correct answer is fat embolism. Most likely, the man fell and fractured his left hip, causing his leg to be shortened and everted (tilted away from midline). Abrupt shortness of breath immediately following fractures is likely due to a fat embolism, which occurs when fat travels from the fracture site (classically long bones) and lodges in the lung blocking venous supply to a portion of the lung, causing deoxygenation and subsequent shortness of breath. This may or may not be detectable with a stethescope. A spiral CT or ventilation/perfusion scan has greater sensitivity and specificity to detect emboli and would likely be the next diagnostic step. (html comment removed: - Explanation )

While venous thromboembolism is possible, fat emboli are more likely given the preceding fracture.

Myocardial infarction is unlikely unless an opening between the venous and arterial blood supply (e.g. a patent foramen ovale) or the patient had documented heart conditions.

Psychogenic stress could explain the vitals signs less the hypoxemia. However, the shortness of breath would not typically come on abruptly.